1. Field of the Invention
This invention relates to an improvement in an optical fiber connector and in one aspect relates to an improved strain relief insert member for coated optical fiber cables for transferring stress on the fiber cable to movement of the fiber toward the connector.
2. Description of the Prior Art
The commercially available splice connectors use a formed end member on each fiber which typically includes a ferrule, a bayonet cover, which overlies a backbone or deformable strain relief member of the connector, and a collapsible strain relief member. The collapsible strain relief insert element is positioned partially within the backbone or strain relief member of the connector. The collapsible strain relief insert element is formed with slots in the terminal end which aid the element to collapse in an even manner. The collapsing terminal end of the strain relief element will grip the optical fiber cable when a crimp ring, placed over the deformable insert element and the strain relief member of the connector, is crimped. Such a structure is disclosed in U.S. Pat. No. 5,425,119 and available from the assignee of this patent (application). The insert element functions to deform around the buffer coating when the crimp ring of the connector is crimped over the insert. This serves to restrain the fiber cable from moving inside the fiber optic connector. Stress on the fiber is transferred to the insert. This area of support separates the stresses that are applied to the cable from being transmitted up the fiber into the connector. The stresses are instead transferred to the insert. Since the volume of the insert gets smaller when it is collapsed onto the fiber by the crimp ring, the material forming the insert tends to flow in the direction of least resistance. In this case the insert is against the connector backbone at one end and therefore its flow is determined by this boundary to be in the opposite direction away from the connector. Since the insert deforms around the fiber, the action of this material flow produces a secondary reaction causing movement of the fiber in the flow direction, away from the connector. The amount of movement depends upon the fiber coating diameter and the insert's outside and inside diameters. If the fiber is not allowed to move with the insert, that is by its being restrained inside of the connector by some means, adhesive, mechanical means, etc., the fiber is placed in a stressed state. This stressed state will cause the connector's performance to decline under outside stresses such as mechanical and environmental forces.
The present invention affords a structured insert which has means for controlling the flow of the insert material resulting in movement of the fiber towards the connector instead of away from the connector.
Improved strain relief resulting in restricted fiber movement and thus no stress onto the fiber through the action of crimping the crimp ring to the backbone, improves the connector performance. The present invention affords such improvements.